Field of the Invention
This invention relates to a system for detecting the open or closed state of a hinged window in an equipment wall. The term "window" is used herein to denote not only a glazed panel, but also any panel which is used to open and close an opening in a wall.
In many pieces of equipment in which a window is provided to open and close an opening in a wall, it is necessary to provide a signal indicating whether the window is open or closed. In many cases it is necessary that the closure of the window should be monitored accurately since, for example, if the "window closed" signal is given before the window is completely closed, malfunctioning of the equipment may occur, or harm may be done to the operator.
It is therefore an object of the present invention to provide a monitoring system which can be made to provide a "window closed" signal only when the window is either completely closed or within a very small distance from the completely closed position.
Most monitoring systems of the kind to which the invention is applicable include a micro-switch which is operated when the window is closed. To obtain accurate monitoring of the closure of the window it is desirable that the micro-switch should be mounted on the movable window assembly, which term window assembly as used herein includes the window and its frame, is mounted as far away as possible from the hinge axis of the window assembly. This means, for example, that in the case of a window which pivots about a horizontal axis at the lower edge of the window the micro-switch would have to be mounted in the region of the upper edge of the window. In such an arrangement the micro-switch plunger would have to engage the equipment wall in such a way that the plunger is depressed by the wall when the window is closed. An arrangement of this kind is frequently impossible for constructional reasons, or at least undesirable for aesthetic reasons.
In cases in which the switch cannot be satisfactorily mounted on the upper edge of the window it has to be mounted in some other position, and a mechanism has to be provided to sense movement between the upper edge of the window and the equipment wall and then transmit this movement to the micro-switch. Most attempts at providing a mechanism of this kind have involved catering for multiple manufacturing tolerances between a number of different components. As a result of these tolerances a system of this kind would entail adjusting the switch position on each individual piece of equipment for satisfactory operation. Arrangements of this kind are therefore normally unacceptable.